Ultra-precision roll turning lathes have recently been developed which achieve ultra-precision machining of a roll for molding a lenticular lens sheet, a cross lenticular lens sheet, a prism sheet, or the like (see, for example, patent document 1).
Such an ultra-precision roll turning lathe includes a tool post having a diamond tool attached thereto, installed on a carriage, and is basically used to machine circumferential grooves in a roll while rotating the roll by means of a headstock and feeding the carriage in a forward-backward direction (X-axis direction). In the case of machining grooves in the axial direction of a roll, the carriage is moved at a high speed in the longitudinal direction (Z-axis direction) of the roll while performing circumferential indexing of the roll (on a C-axis) with the headstock. In this manner, grooves can be created in the axial direction of the roll.
The use of such an ultra-precision roll turning lathe can machine with precision numerous grooves, e.g. having a pitch of 50 μm and a depth of 25 μm, in the surface of a roll in the circumferential or longitudinal direction of the roll.